1. Field of the Invention
The present invention relates to a touch panel. More specifically, the present invention relates to a touch panel wherein cells to perform sensing operation are partitioned into a plurality of portions, a plurality of electrodes are divided in the portions, and the electrodes are connected to each other through one routing line to improve touch sensitivity, and a method for fabricating the same.
2. Discussion of the Related Art
In recent years, there is an increasing need for a touch panel wherein a touched portion is sensed by the hand or separate input means and additional information can be transferred in response to the touch. Such a touch panel is adhered to the external surface of a liquid crystal display.
Depending on the touch sensation type, touch panels are classified into resistive touch panels, capacitive touch panels and infrared (IR) touch panels. Owing to factors such as convenience of fabrication and sensitivity, capacitive touch panels attract much attention.
Hereinafter, a conventional capacitive touch panel will be illustrated with reference to the annexed drawings in detail.
FIG. 1 is a plan view illustrating a conventional touch panel and FIG. 2 is an enlarged view of the region A of FIG. 1.
As shown in FIGS. 1 and 2, a conventional capacitive touch panel comprises a substrate 10, and a plurality of rows of first electrodes 11 and a plurality of rows of second electrodes 12 arranged on the substrate 10 such that they cross each other. The touch panel comprises a pad electrode 40 connected to a flexible printed circuit (FPC) 50 including a touch controller 51 at one side of the substrate 10. The row of the first electrode 11 and the row of the second electrode 12 are connected to the pad electrode 40 through a routing line 25.
The rows of the first electrodes 11 cross rows of the second electrodes 12 in the form of bars. Alternatively, as illustrated in the drawings, the rows of the first and second electrodes 11 and 12 are in the form of diamond patterns in respective sensing regions, the second electrodes 12 are formed such that they have a thin connection pattern integrated with adjacent diamond patterns, and the first electrodes 11 are electrically connected through a connection metal pattern 21 of adjacent diamond pattern and metal in the different layer with respect to the interconnection pattern.
The touch controller 51 is a form of integrated circuit (IC), which is provided at one side with input pins as connection portions to an operating portion of a display device and at the other side with output pins (not shown, which contacts the pad electrode 40) to apply signals to the first and second electrodes 11 and 12.
Respective ends of the rows of the first electrode 11 and rows of the second electrode 12 are connected to the routing line 25 and thus connected to the pad electrodes 40.
In FIG. 1, both ends of the first electrode 11 are connected to the routing line 25. This configuration is designed so that both ends of the first electrode 11 can receive signals in order to reduce differences in RC delay between both ends thereof. In some instances, the routing line may be connected to only one end of the first electrode 11.
For a conventional touch panel in all of these instances, at least one routing line is connected to each of the first electrode 11 and the second electrode 12.
Meanwhile, as shown in FIG. 2, in recently mass-produced touch panels, diamond patterns constituting the first electrodes 11 and the second electrodes 12 have a diagonal line of 6 to 10 mm, and the distance between the first electrode 11 and the second electrode 12 adjacent to each other is 300 μm or greater.
FIG. 3 is a view illustrating failure caused by multi-touch of a conventional touch panel.
A conventional touch panel is touched by an input means such as the finger. The surface of the touch panel is rapidly touched several times by the finger in an oval or circular motion and whether or not the touch is sensed is confirmed. As a result, the drawn lines are partially interrupted, as shown in FIG. 3. In addition, a ghost error wherein a region not touched by the finger is detected, when different regions are touched, occurs.
Such a failure is due to small variations in capacitance before and after touch and the reasons therefor are as follows.
The capacitive touch panel of FIGS. 1 and 2 detects the presence of touch by setting a predetermined threshold electric charge to a system and deciding a region having an electric charge exceeding the set value to be touched.
In this instance, a fringe field is generated between the first and second electrodes 11 and 12 spaced from each other and the finger varies the fringe field present therebetween. Practically, an initial fringe field is greatly varied, when an area provided between the first and second electrodes 11 and 12 is touched, whereas an electric charge does not exceed the threshold electric charge due to slight variation in initial fringe field and thus small variation in electric charge before and after touch, when the center of the first electrode 11 or the second electrode 12 is touched. As a result, interruption of touch occurs.
In addition, variations in electric charge before and after touch are great at the center of the first electrode 11 and the second electrode 12, and touch sensitivity is improved with increasing proximity to the center of a touched position. However, a region touched by the finger may be 10 mm or smaller and touch sensitivity thereof is thus deteriorated, as a touched portion becomes farther from the center of the first electrode 11 and the second electrode 12 (closer to the center thereof). In particular, relative touch sensitivity of a predetermined region is deteriorated and detection of touch is impossible in a portion of region where the electrodes are formed.
In addition, ghost phenomenon may occur due to malfunction of touch detection upon multi-touch and the reason therefor is considered to be deterioration in touch sensitivity.
Such conventional touch panel has the following problems.
The conventional touch panel comprises a plurality of first and second electrodes crossing each other, and compares variation in electric charge induced by a fringe field between the first electrode and the second electrode with a threshold electric charge set in a system, to detect presence of touch.
In this instance, when a critical value of the first electrode and the second electrode is high, as compared to a contact area of the finger, touch sensitivity is deteriorated with increasing proximity to the center of the electrode. At this time, touch cannot be detected due to an electric charge lower than a threshold electric charge at the center of electrodes upon touch. This is observed as breakdown or ghost upon multi-touch.
In some instances, in order to increase variations in fringe field between the first and second electrodes before and after touch, an insulating film with a predetermined thickness or greater may be further provided between the panel surface on which the finger contacts the first and second electrodes. However, formation of the insulating film requires a material and mask process, thus disadvantageously causing inconvenience due to increased cost and variation of apparatus to install the touch panel.